Propeller bosses



' May 27, 1969 J. H. ATTWOOD 3,446,290 v PROPELLER BOSSES Original FiledNov. 22, 1966 Sheet of 2 FIG. 7.

.l. H. ATTWOOD INVENTOR I May 27, 1 J. H. ATTWOOD PROPELLER BOSSES Sheet012 Original Filed Nov. 22, 1966 J. H. ATTWOOD mvsu United States PatentUS. Cl. 170-173 16 Claims ABSTRACT OF THE DISCLOSURE The disclosure ofthe instant invention relates to an improved propeller shaft assemblycomprising a propeller shaft provided with an internal radial flangeconnected to an internal radial flange of a hollow propeller boss. Theshaft and propeller boss are connected together by fastening elementswhich pass through apertures in the flanges of both the propeller shaftand propeller boss; said fastening elements being housed entirely insidethe boss and shaft.

This application is a continuation of Ser. No. 596,190, filed Nov. 22,1966.

This invention relates to the connection of propeller bosses topropeller shafts.

In the past propeller bosses have usually been attached to propellershafts in two ways. In one case, the boss has an external flange andthis flange is bolted to an external flange at the end of the propellershaft. The disadvantage of this arrangement is that the bolts are inconstant contact with sea water and corrosion is likely to occur; inaddition due to the external flange the propeller shaft cannot beremoved inboard but must be removed outboard. In an alternative way offixing the boss to the propeller shaft, the end of the shaft is taperedand the boss is slipped over the tapered portion of the shaft and fixedto the shaft by a key and nut. The disadvantage of this arrangement isthat not only are there shear stresses but also there are hoop stressesof uncontrolled size on the shaft and boss; and in larger sizes ofpropeller, fitting problems arise together with large overhung weightsgiving high bending stresses and deflections in the propeller shaft.

According to this invention these disadvantages are eliminated orobviated by a propeller shaft assembly comprising a propeller shaftconnected to an internal radial flange of a hollow propeller boss, saidshaft and boss being connected together by fastening elements passingthrough apertures in said flange wherein said elements are housedentirely inside the boss and shaft. The shaft and the boss can beconnected together in a butt joint with a known and controlledcompressive stress. The use of a hollow boss reduces the Weight andminimises shaft bending stresses and deflections. Also as a result ofthe invention the fastening elements are housed inside the boss andshaft and are not exposed to sea water, there is no external flange sothat after removal of the propeller from the shaft, the shaft can oftenbe removed inboard, and also there are not fixing hoop stresses, set upin boss and shaft.

The outer diameter of the propeller boss is preferably slightly largerthan the outer diameter of the propeller shaft, to allow fitting of astern tube oil seal and a rope guard. Preferably the propeller boss isintegral with the propeller blades, but this need not be so.

The boss may have internal longitudinal ribs, for example four innumber, and may often have an internal flange intermediate of the endsthereof, additional to the internal radial flange. When the fasteningelements are introduced into the apertures of the flange from inside thepropeller boss this additional intermediate flange should be spaced fromthe internal radial flange by a distance at least equal to the length ofthe fastening elements. There may if desired be another internal radialflange (hereinafter referred to as the second internal radial flange)situated at the other end of the boss, and this flange will facilitatethe attachment of a fairwater cap closing plate to the end of the bossremote from the propeller shaft.

The fastening elements are preferably bolts, to which nuts are attached.However, in certain circumstances it may be desirable to use studs, orrods having two screwed ends to which nuts may be attached.

The internal radial flange with apertures thereon, for example sixteenin number, preferably extends continuously around the inside of the endof the boss, and when bolts are used as fastening elements the radiallength of this flange is preferably greater than the diameter of theheads of the bolts used in fastening the boss to the propeller shaft.

The fastening elements also preferably pass through apertures in thepropeller shaft, and the shaft which is preferably hollow, is thereforepreferably provided at its tail end with an internal flange having aplurality of apertures therein. The internal flange on the shaftpreferably has a spigot extending outwardly beyond the shaft, in anaxial direction, the outer diameter of which spigot is substantiallyequal to the internal diameter of the internal radial flange on theboss, so that when the boss and propeller shaft are connected to oneanother the spigot on the shaft makes a guide fit with the internalradial flange on the boss. The fit between spigot and flange should notbe so tight that shaft and boss have to be connected together only undervery carefully controlled conditions. When bolts are used in fasteningthe boss to the propeller shaft, the heads of the bolts may rest againstthe inner surface of the internal radial flange on the boss, and thebolts are then fastened at their other ends inside the shaft, e.g., bynuts or by being screwed into screw threads provided in the propellershaft. However, in some circumstances it may be desirable or possible toreverse this arrangement, so that the heads of the bolts abut a flangeprovided internally at the end of the propeller shaft.

In a preferred embodiment of the invention the propeller shaft itselfhas an extra internal flange spaced a short distance axially from itsinternal flange at the tail end of the shaft. Preferably the internalsurface of the shaft between the two flanges is smoothly curved in anaxial direction. In such cases the fastening elements, e.g., bolts, passthrough both flanges inside the shaft, and are made fast, e.g., by nuts,at the internal radial flange of the propeller boss.

In a preferred embodiment of the invention when bolts are used, thespaces between the shanks of the bolts and the walls of the apertures onthe flanges in the boss and shaft are occupied by sleeves or hollowdowels, so that the dowels or sleeves take all the shear and bendingloads whilst the bolts are in tension only. It is further intended thateach bolt shall be preloaded equally and to such a known degree that thetotal compressive load between the abutting flanges of the shaft andboss shall be well in excess of any separating forces, e.g., propellerand stem thrusts.

Once the boss has been fastened to the propeller shaft, the end of theboss remote from the shaft can be closed, e.g., by attaching a fairwatercap.

Preferred embodiments of the invention are described 3 with reference tothe accompanying drawings in which:

FIGURE 1 shows a half longitudinal sectional view of a propeller bossand its attachment to the propeller shaft;

FIGURE 2 shows a sectional elevation on a larger scale of a hollowdowel;

FIGURE 3 shows a cross-sectional elevation through the line IIIIII ofFIGURE 1;

FIGURE 4 shows a sectional elevation through the line IVIV of FIGURE 1;

FIGURE 5 shows a half longitudinal sectional view of an alignment doweltogether with its adaptor;

FIGURE 6 shows a half longitudinal sectional view of a propeller bossattached to a propeller shaft, alternative'to that shown in FIGURE 1;

FIGURE 7 shows a part sectional elevation on a larger scale of acoupling bolt used in the arrangement shown in FIGURE 6;

FIGURE 8 shows a sectional elevation of a hollow dowel used in thearrangement shown in FIGURE 6;

FIGURE 9 shows half cross-sectional elevations through the lines AA andBB of FIGURE 6; and

FIGURE 10 shows a full cross-sectional elevation through the line C'C ofFIGURE 6.

Referring to FIGURES l to 4 of the drawings, the propeller boss 1 withpart of the propeller shown at 1a has an internal radial flange 2, anintermediate flange 3, and a second internal radial flange 4. There arefour longitudinal ribs 5, 6, 7 and 8 on the inside of the boss 1, andalso four longitudinal ribs 9, 10, 11 and 12 on the inside of thepropeller shaft 13. The propeller shaft 13 has a flange 14 with a spigotportion 15. The external diameter of the spigot portion 15 issubstantially equal to the internal diameter of the flange 2, so thatspigot and flange make a guide fit.

The flange has sixteen circular apertures which cooperate with sixteencircular apertures in the flange 14 of the propeller shaft 13, therebyforming sixteen common circular apertures 17.

Before fastening the propeller boss 1 to the propeller shaft for thefirst time it may be necessary after aligning the apertures in theflanges of boss 1 and shaft 13 to ream the apertures. This may beaccomplished by the use of a reamer, and for this purpose theintermediate flange 3 can be used as a backstop. When the apertures havebeen reamed when this is necessary, the boss 1 can then be fastened tothe shaft 13.

Into the apertures 17 hollow shear dowels 19 are inserted making aninterference fit and they thereby act as sleeve surrounding the shaft ofthe bolts. The bolts 18 are then inserted and landing collars 20 arefitted on the bolts, followed by nuts 21 thereby forcing the boss 1 andshaft 13 together, so that the heads 16 of the bolts 18 abut the flange2. An annular oil seal 22 may then be fitted round the junction of theboss 1 and the shaft 13.

Finally, plate 23 and closing plate 24 are secured to the shoulder 15 ofthe flange 14, and to the flange 4 respectively, and then a fairwatercap 25 is fixed to the boss 1.

Referring to FIGURE 5 of the drawings, the alignment dowel has a taperedportion 31 and an adjustable threaded portion 32. The diameter of themain portion 33 of this dowel is substantially the same as that of theapertures in the shaft and boss. The dowel also has a flanged portion34, so that when the dowel is inserted into the apertures in the shaftand boss, this portion 34 corresponds to the heads 16 of the bolts. Alsoshown in FIG- URE 5 is an adaptor 35 which may be screwed into the dowel30 when located in position in the apertures in the shaft and boss. Thisadaptor 35 has an external thread 36 onto which nuts can be threaded soas to connect shaft and boss firmly when the alignment dowel and adaptorare in position in the apertures of the shaft and boss.

In practice the boss 1 and shaft 13 can be temporarily connectedtogether by inserting temporary bolts into alternate apertures, andscrewing nuts onto the ends of the bolts. The alignment dowels 30 arethen'introduced into the remaining unoccupied apertures and adaptors 35and nuts attached by the method described above. The boss 1 and shaft 13are then firmly connected together with the apertures 17 in truealignment. The temporary bolts can then be removed, hollow dowels 19introduced into the apertures and the permanent bolts 18 inserted andmade fast by collars 20 and nuts 21. The alignment dowels 30 can then beremoved, and hollow dowels 19 introduced into these vacated apertures,followed by the bolts 18 which are made fast 'by colars 20 and nuts 21.

Referring to FIGURES 6 to 10 of the drawings, parts which are identicalto those described with reference to FIGURES 1 to 5 of the drawings areindicated with identical numerals. In this case the propeller shaft 40is shaped differently and has an internal flange 41, and the innersurface of the shaft 40 is smoothly curved between this flange 41 andthe spigot portion 42 of the shaft 40, thereby eliminating any stressconcentrations which would result from sharp corners. Also in this casethe propeller boss has no internal ribs.

The coupling bolts which are used are shown in FIG- URE 7, and it can beseen that they have a raised portion 44 which gives an aver-age runningfit when inserted in the dowel 45. In this particular arrangement theheads 46 of the bolts are inside the propeller shaft 40 and not insidethe propeller boss 1. The other ends of the bolts 43 are secured bymeans of nuts 47 and washers 48, these washers having a portion ofsmaller internal diameter which fits inside the apertures 17.Surrounding the shanks of the bolts 43 are hollow dowels 45 which inthis case have an internal threaded portion 49. The dowels 45 may beremoved by using a conventional form of stud withdrawing gear modifiedhowever to allow for the fact that the dowel 45 has an internal threadrather than an external thread as is usually the case with studs.

The propeller boss and propeller shaft can be connected together in asimilar manner to that described with reference to FIGURES 1 to 4 of thedrawings, except that the direction of the bolts is reversed. Aligningdowels 30 would be used without adaptor 35 in a similar manner to thatdescribed with reference to FIGURE 5 of the drawings. This particulararrangement shown in FIGURES 6 to 10 is advantageous compared with thatshown in FIGURES 1 to 4 of the drawings because the tail end of thepropeller shaft has been redesigned so as to reduce any possible stressconcentrations. This arrangement does however require the use of longerbolts.

What is claimed is:

1. A propeller and propeller shaft assembly for a marine vesselcomprising a propeller shaft and a propeller including a hollowpropeller boss with an internal radial flange having apertures therein,fastening elements passing through the apertures in said flange so as toconnect said shaft to said flange, wherein said elements are housedentirely inside the boss and shaft, and closure plate means sealing theend of said boss opposite said flange to thereby exclude sea water fromsaid fastening elements and prevent corrosion thereof, said fasteningelements comprising bolts and nuts attached thereto, said bolts beingsmaller than said aperatures, and hollow dowels interposed between saidbolts and the walls of the apertures in the rflanges of the boss andshaft, said hollow dowels having an internal diameter greater than thediameter of said bolts, so that said dowels take all the shear loadswhile the bolts are in tension only.

2. An assembly as claimed in claim 1 wherein the boss has internallongitudinal ribs.

3. An assembly as claimed in claim 1 wherein the boss has an internalflange intermediate of the ends thereof.

4. An assembly as claimed in claim 3 wherein the boss has a secondinternal radial flange situated at the end of the boss remote from theinternal radial flange.

5. An assembly is claimed in claim 1 wherein the boss has foursymmetrically disposed longitudinal ribs and four circular apertures ineach quadrant bounded by the ribs.

6. An assembly as claimed in claim 1 wherein the propeller shaft ishollow.

7. An assembly as claimed in claim 3 wherein the fastening elements arebolts and the intermediate internal flange of the propeller boss isspaced from the internal radial flange of the boss abutting thepropeller shaft by a distance at least equal to the length of the bolts.

8. A propeller and propeller shaft assembly for a marine vesselcomprising a propeller shaft, said shaft having at its tail end aninternal flange having a plurality of apertures therein and a propellerincluding a hollow propeller boss with an internal radial flange havingapertures therein, fastening elements passing through the apertures insaid flanges so as to connect said shaft to said boss, and closure platemeans sealing the end of said boss opposite said boss internal radialflange to thereby exclude sea water from said fastening elements andprevent corrosion thereof, said fastening elements comprising bolts andnuts attached thereto, said bolts being smaller than said apertures, andhollow dowels interposed between said bolts and the walls of theapertures in the flanges of the boss and shaft, said hollow dowelshaving an internal diameter greater than the diameter of said bolts, sothat said dowels take all the shear loads while the bolts are in tensiononly.

9. An assembly as claimed in claim 8 wherein there is a spigot extendingoutwardly beyond flange on the shaft, the outer diameter of the spigotbeing substantially equal to the internal diameter of the internalradial flange on the boss.

10. An assembly as claimed in claim 9 wherein there is an extra internalflange axially spaced a short distance from the flange at the tail endof the propeller shaft.

11. An assembly as claimed in claimed 10 wherein the internal surface ofthe shaft between the two flanges is smoothly curved in an axialdirection.

12. An assembly as claimed in claim 1 wherein said dowels makeinterference fits with the apertures.

13. An assembly as claimed in claim 1 wherein the outer diameter of thepropeller boss is slightly larger than that of the propeller shaft.

14. A bladed propeller and propeller shaft assembly for a marine vesselcomprising a propeller shaft having an internal radial flange and apropeller including a hollow propeller boss with a radial flange havingapertures therein, fastening means for connecting said propeller shaftflange and said boss flange, said fastening means passing through saidapertures and being smaller in diameter than said apertures, saidfastening means being housed entirely inside said boss and said shaft,and dowel members interposed between said fastening means and the wallsof said apertures, said members having an internal diameter greater thanthe diameter of said fastening means so that said dowels take all theshear loads while the fastening means are in tension only.

15. A propeller and propeller shaft assembly for a marine vesselcomprising a propeller shaft and a propeller including a hollowpropeller boss with an internal radial flange having apertures therein,fastening elements pass ing through the apertures in said flange so asto connect said shaft to said flange, wherein said elements are housedentirely inside the boss and shaft and wherein when said shaft and bossare fastened together no part of said fastening elements protrude into asurface of said shaft or boss which comes into contact with sea water,and closure plate means sealing the end of said boss opposite saidflange to thereby exclude sea water from said fastening elements andprevent corrosion thereof.

16. The assembly of claim 15 further characterized in that dowel membersare interposed between said fastening elements and the walls of saidapertures, said dowel members having an internal diameter greater thanthe diameter of said fastening means so that said dowels take all theshear loads while the fastening means are in tension only.

References Cited UNITED STATES PATENTS 2,028,448 1/1936 Harza -160.232,470,517 5/1949 Obrist. 2,987,123 6/1961 Liaaen. 3,228,482 1/1966Bunyan.

FOREIGN PATENTS 459,988 1/ 1937 Great Britain.

EVERETTE A. POWELL, JR., Primary Examiner.

US. Cl. X.R. 170159, 160.23

